8520 themes run just fine on my 8350, no problems at all. The operating system is the same for both at 4.6xx unless the 8520 had the OS upgraded to 5.0, then I can't say not having tried that yet...maybe others have.

The 8520 should be able to use 8350 themes as well, maybe one of the 8520 theme seekers can give that a go??